Unresponsive throttle?

[Neith]

I recently had my car (JDM Spec-R) serviced at JM Imports; the guy who did the work said that the throttle felt less responsive than other S15s they've had in. The car is totally stock at present, from 2nd gear upwards it boosts to 0.6bar but feels initially a bit unresponsive. I'd never thought anything of it as I've never owned a turbo before and assumed it was pretty normal.

I have noticed lately that I need a bit more accelerator pedal travel than usual to pull away smoothly, otherwise the car feels like it wants to bog down. It never feels like it wants to stall but feels lethargic and like it's possibly down on power.

I still only know really basic things mechanically so I just wanted some ideas of what could be causing it before I take it back to JM if needed. Is 0.6 bar normal for a stock JDM S15? I know 0.7 is the usual figure but would 0.6bar be treated as close enough to normal or indicating a problem somewhere?

Cheers for any help, it's probably something really obvious but wanted to ask here first in case it's a common problem (saw a few other threads but not sure if they relate to this problem).

 

[2fst4u]

The boost level is fine first thing that comes to mind for me is to check the throttle cable is still secure in the bracket on the intake manifold. Simple stuff first

 

[NathF]

Mine only boosts to 0.4 bar!

 

[2fst4u]

Stock boost is 7psi isn't it? That's roughly .5 .6 bar

 

[spoonman]

throttle response can have a huge impact from how you have setup your intake system, how heat soaked your intercooler is getting (not enough airflow), far too large intercooler piping, if your tps is adjusted wrong and it does not reach the throttle closed moving to open voltage until way to far into the butterfly's opening movement, if your pedal has heaps of freeplay or slop, having a collapsed CAT or muffler.
Whilst moving throttle response can be affected more by having a poorly set up pressure feed to your wastegate.

 

[spoonman]

Mine only boosts to 0.4 bar!

something is wrong....... really wrong with your setup

.4 bar is what you would get with a intercooler the size of the palm of your hand...... and a exhaust the diameter of a mouse

 

[Neith]

throttle response can have a huge impact from how you have setup your intake system, how heat soaked your intercooler is getting (not enough airflow), far too large intercooler piping, if your tps is adjusted wrong and it does not reach the throttle closed moving to open voltage until way to far into the butterfly's opening movement, if your pedal has heaps of freeplay or slop, having a collapsed CAT or muffler.
Whilst moving throttle response can be affected more by having a poorly set up pressure feed to your wastegate.

The intake setup/intercooler piping is all standard, the car isn't modified at all. The accelerator pedal does feel as if I need to press it a little (maybe an inch or so?) before I get any response (as if there's some play in the pedal). I wasn't sure if this was typical of S15s though so it never really stood out until now.

Out of everything you've said, the pedal freeplay sounds the most likely. Is there any way of adjusting it?

Thanks for the replies everyone, trying to learn the basics so I don't feel like I need to take it to a garage for everything :wack:

 

[fez06]

Adjust the nuts on the cable next to the throttle body and take out the slack.

 

[spoonman]

Adjust the nuts on the cable next to the throttle body and take out the slack.

This ^^^^

 

[2fst4u]

Goddamnit I basically said that

 

[S15_SAM]

Um no you didn't?! Lol! You said make sure the cable is still connected! Also you said stock boost is 7psi, we don't work in that archaic measurement, we use bar! stock setup is 0.7 after 3.5-4kRpm

 

[2fst4u]

Um no you didn't?! Lol! You said make sure the cable is still connected! Also you said stock boost is 7psi, we don't work in that archaic measurement, we use bar! stock setup is 0.7 after 3.5-4kRpm

I said "secure". Not "connected". If it isn't tight enough then it will have play and therefore won't be secure while still connected to the bracket.

I also said 7 psi = .5 /.6 bar. I think you'll find stock boost is .5 bar which is in fact just over 7psi. My numbers came from the manual, yours clearly didn't.

 

[Clarkey]

The only English manual is for the ADM though which is less powerful than JDM. No way you will make 250ps on 0.5bar.

 

[NathF]

Any reason why mine will be down on boost? Apart from usual boost leaks and turbo wear

 

[Clarkey]

Leak, wastegate weak, wastegate solenoid not working.. Superclarkey at doritech has a guy with a posh smoke boost leak checker, give him a call and have it checked. It must be slow on 0.4bar, they are pretty mediocre on 0.6, it's only really party time when you get to 1.0 or more.

 

[NathF]

Nice one, cheers buddy
yeah it isnt the fastest thing ive driven lol, only got a 15.4 at santa pod. My 219bhp astra got a 14.6. Done the free boost mod and i touch 0.5 bar now

 

[Clarkey]

Too bad, but trust me get 1bar into it and you will love it.

 

[Neith]

I've taken some of the slack out of the cable and the response does seem a bit better now. Probably further tweaking required though.

When I was adjusting it, one of the rubber circular rings (the one nearest the throttle drum) came off. It looks like one side was stuck on with something that has since rotted away. It's still relatively secure at the minute but I just wondered what it's actually for (restricting the slack in the cable?).

Thanks for all the help!

 

[2fst4u]

I've taken some of the slack out of the cable and the response does seem a bit better now. Probably further tweaking required though.

When I was adjusting it, one of the rubber circular rings (the one nearest the throttle drum) came off. It looks like one side was stuck on with something that has since rotted away. It's still relatively secure at the minute but I just wondered what it's actually for (restricting the slack in the cable?).

Thanks for all the help!

The grommet that goes between the two washers?

 

[spoonman]

I said "secure". Not "connected". If it isn't tight enough then it will have play and therefore won't be secure while still connected to the bracket.

I also said 7 psi = .5 /.6 bar. I think you'll find stock boost is .5 bar which is in fact just over 7psi. My numbers came from the manual, yours clearly didn't.

Whats wrong with us aye..........

New Zealand is a country that uses metric for everything ks, weight and all that apart from pressure so we use psi not bar
England is a country the uses imperial for everything miles, money, weight but they calculate pressure in kgm2 (bar)